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(NoMddeL) I H. ALABASTER 81; T. E. GATEHOUS'E. TELEPHONE TRANSMITTER.

No. 335,791. Patented Feb. 9, 1886.

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TELEPHONE TRANSll/HTTER.

' SPECIFICATION forming part of Letters Patent No. 335,791, dated February 9, 1886.

Application filed May 14, 1885. Serial No. 165,427. (No model.) Patented in England January 11, 1883, No. 179, and in France July 10, 1383, No. 156,510.

To all whom it 10mg concern.-

Be it known that we, HENRY ALABASTER and Tom ERNEST GATEHOUSE, subjects of the Queen of Great Britain, and residents of London, England, have invented certain new and useful Improvements in Telephone-Transmitters, (patented also in England January 11, 1883, N0. 179, and in France July 10, 1883, No. 156,510,) of which the following is a specification.

Our invention relates to improvements in telephone=transmitters, but more particularly to that part of the transmitter which has come to be called the tension-regulator. V

The object of the invention is to provide a tension regulator for telephone transmitters which is more sensitive to the vibrations of acoustic impulses than those heretofore in vented.

Herctofore tension-regulators in telephonetransmitters have consisted of two or more pieces of carbon in contact with one another. The surfaces of contact have been made smooth, in order to increase the efficiency. In order to maintain the electrodes in contact,they have been so arranged that one will bear upon the other by its own weight, or by a spring, or by a brace or prop, or by levers and springs. \Vhen subjected to the influence of air-vibrations, or to any form of acoustic impulses, the resistance of the circuit is increased and diminished alternately in such a manner as to produce an undulatory current. This undulatory current should be as nearly as possible in unison as regards the number and ampli tude of vibrations with the acoustic impulses. It is evident that the production of the undulatory current depends upon the nature of the tension-regulator. More than this, it depends more particularly upon the nature of the contact-surfaces of the carbon electrodes.

Our invention consists in such a construction that the surfaces of the electrodes are held in the proper position in a superior manner.

In order that our invention may be clearly and practically understood, the accompanying drawings are added in order to show the transmitter which is best adapted to embody the present invention.

Figure 1 is a general outside view of the 5 transmitter. Figs. 2 and 3 are sectional views, with a mouth-piece attached in Fig. 2.

A is an insulating-base, preferably of hardened plaster, into which are buried the two electrodes B and G, of carbon, whose upper surfaces are preferably smooth to the point of polish. The upper surfaces of O and B, or

per part of A by means of cement or otherwise, so that the carbon disk D, being little smaller in diameter than the inner diameter of the annulus F, rests upon the electrodes B and O with a force greater than its own weight, the extra force being that of cohesion. The piece F is of insulating material, preferably of hard rubber. To the top surface of the annulus F is secured the mouth-piece H by screws J.

The operation is as follows: The current passes through the two electrodes by way of the contact-surfaces between the carbon disk D and the said electrodes. When the tube H conveys acoustic impulses or vibrations, the disk D is pressed alternately with a strong and a weak force against the electrodes, and yet it is always in contact with the electrodes at each point, because there is not a layer of air between them, as would be the case if the force of cohesion were not perceptible.

The force of cohesion varies inversely as the square of the distance, and within limits which may be defined thus: between actual contact of the surfaces at theoretically every point and contact of the surfaces at practically every point. Within these limits the force of cohesion acts, and within these limits the vibrations due to acoustic impulses occur.

\Ve claim-- In a telephone-transmitter, the combination of the following elements: the two car bon electrodes Band 0, buried in the insulating substance A, the carbon bridge D, resting upon both electrodes, the surfaces of conpresenceof two witnesses, this 18th day of tact between the electrodes and bridge being March, 1885.

plane and smooth to the point of p01ish,and the HENRY ALABASTER. ring F, secured to A, and surrounding the TOM ERNEST GATEHOUSE. 5 bridge D, substantially as described. WVitnesses:

In testimony that we claim the foregoing as SAM P. WILDING, our invention we have signed our names, in JOHN 0. FALL. 

